1. Field of the Invention
The present invention relates to a hinge assembly for rotationally attaching a first member to a second member to allow rotational movement of the first member relative to the second member that provides for increased resistance to relative rotation between the first member and the second member at one or more predetermined angular positions of the first member relative to the second member.
2. Description of the Prior Art
Hinge assemblies for rotationally attaching a first member to a second member to allow rotational movement of the first member relative to the second member are known in the prior art. Furthermore, hinge assemblies that provide for increased resistance to relative rotation between the first member and the second member at one or more predetermined angular positions of the first member relative to the second member are also known in the prior art. Examples of such hinge assemblies, known in the art as detent hinges, can be seen in U.S. Pat. No. 5,412,842 issued to Allen Riblett, on May 9, 1995, U.S. Pat. No. 6,941,617 B2 issued to Ana Christina Pinto, on Sep. 13, 2005, U.S. Pat. No. 7,320,152 B2 issued to David A. Lowry et al., on Jan. 22, 2008, U.S. Pat. No. 6,141,831 issued to Eugene Novin et al., on Nov. 7, 2000, U.S. Pat. No. 7,065,834 B2 issued to David A. Lowry, on Jun. 27, 2006, and U.S. Pat. No. US 5,765,263 issued to Andres A. Bolinas et al., on Jun. 16, 1998.
In general, hinges have a first hinge part adapted for attachment to a first hinged member and a second hinge part adapted for attachment to a second hinged member. A hinge shaft supports the first and second hinge parts for rotation relative to one another, which in turn provides for relative rotation between the first and second hinged members. The phrase “hinged members” refers to the first and second members that are connected together using the hinge such that they can rotate or pivot relative to one another. Detent hinges have an additional function that provides for increased resistance to relative rotation between the first hinge part and the second hinge part at one or more predetermined angular positions of the first hinge part relative to the second hinge part in order to provide for the holding of the first hinged member at one or more desired angular positions relative to the second hinged member. This additional function is what is referred to as the detent function of the hinge.
U.S. Pat. Nos. 5,412,842 and 6,941,617 B2 show detent hinges that use coil springs that are positioned to extend transversely relative to the longitudinal axis of the hinge shaft to bias members such as ball bearings into engagement with grooves in the hinge shaft in order to provide for the detent function of the hinge. The space needed for the coil springs which extend laterally relative to the hinge shaft prevents these prior art hinges from being compact enough for certain applications.
U.S. Pat. Nos. 7,320,152 B2, 6,141,831, and 7,065,834 B2 show detent hinges that use coil springs that fit around the hinge shaft and that extend longitudinally along the hinge shaft. The spring biases a cam that can slide back and forth along a direction coincident with the longitudinal axis of the hinge shaft. The cam is prevented from rotation relative to one of the first and second hinge parts, which for the sake of convenience we will designate the second hinge part. Usually this would be the hinge part that houses the spring. The cam has one or more protrusions that engage corresponding depressions provided in the other hinge part, which in this case would be the first hinge part, in order to provide for the detent function of the hinge. This type of detent hinge can be made in a very compact size; however, this type of detent hinge has the disadvantage that its parts are exposed to sliding friction, which can cause faster wear as compared to the ware due to the rolling friction of the ball bearings in the previous type of prior art detent hinge.
U.S. Pat. No. 5,765,263 shows a third type of prior art detent hinge. In this type of hinge, a member is biased to project radially outward from the hinge shaft. The hinge shaft is fixed to the second hinge part and extends into a bore in the first hinge part such that the first hinge part can rotate on the hinge shaft. The member projecting radially from the shaft engages one or more grooves in the bore of the first hinge part in order to provide for the detent function of the hinge. This type of detent hinge cannot be made compact enough for some applications because the hinge shaft must be large enough in size, both in terms of diameter and length, to house the radially projecting member. This type of detent hinge has the additional disadvantage that its parts are exposed to sliding friction, which can cause faster wear as compared to the ware due to the rolling friction of the ball bearings used in the first type of prior art detent hinge.
None of the prior art hinge assemblies are seen to teach or suggest the unique features of the present invention or to achieve the advantages of the present invention.